Fair Head Tidal (FHT), a development company set up by DP Marine Energy (DPME) and DEME Blue Energy (DBE), proposes to build a tidal energy development of up to 100MW installed capacity off Fair Head in North Antrim in Northern Ireland.
The project received an “Agreement for Lease” (AfL) from The Crown Estate (TCE) on the 10th October 2012. The AfL allows the developer exclusive rights to develop a tidal energy site off Fair Head. The planning application for the project was submitted in February 2017. If, following consultation and environmental impact assessments, the proposal is consented the build programme for phase 1 (four to sox turbines depending on turbine capacity) is due to begin in Q2 of 2018 and is planned to be operational by the end of the year, although this will depend heavily on resolving onshore grid connection issues.
The area of development lies within the Rathlin Island and Torr Head Strategic Area 2km east of Fair Head. The site occupies a total area of approximately 4.2km2 and is around 1km off the North Antrim Coast in Northern Ireland.
Grab samples collected by the British Geological survey indicate that the seabed in this area is an extensive rocky outcrop supporting some gravelly sediments, with the majority of the area from Fair Head to Torr Head being shallow course sediment plains. Water depths vary from 25 to 130m with a steep slope being present 50m from the headland. This extends out to 1km and the gradient levels off at a depth of around 120m 4km from the coast line.
The proposal is based on a technology neutral approach. Given the physical constraints and resources of the development site, an envelope has been developed based on a generic design philosophy using horizontal axis tidal turbines with open rotors. The envelope allows for both floating moored and seabed mounted systems which may be surface piercing or non-surface piercing.
Example devices include the Siemens MCT SeaGen S, the Alstom TGL, Voith Hydro and Hammerfest Strom. Currently there is no practical experience for turbine spacing, however analytical models are being produced and preliminary layouts or the array are based on spacing’s of 500m down-stream and 150m across. Rotor diameter will be limited by water depth.
Inter array cables:
Individual turbines will be connected to one or more subsea or surface mounted marshalling units containing both power conditioning equipment and transformers in order to increase the generated voltage to 33kV for transmission without significant losses. It is unlikely that a further step up in voltage to 110kV or 132kV will be necessary. Subsea substations at this scale are still unproven, and consequently the project approach is to utilise surface piercing solutions such as the SeaGen S Mark 2 or floating devices to provide the marshalling points for the farm. The advantage of this approach is that principle connections can be undertaken dry with no requirement for underwater connections or the placement of key electrical equipment on the seabed.
The detailed electrical design is yet to be completed but it is likely that multiple 33kV cables will be used to deliver the 100MW capacity to shore. The Fair Head project is relatively close to the mainland, hence lower voltage cables can be utilised with minimal transmission losses. Additionally there is no requirement for a dedicated high voltage and expensive offshore transformer station. As far as possible, cable routes will avoid traversing areas of very high tidal flow and will be either trenched, pinned or protected by rock dumping or mattresses depending on the seabed characteristics. Installation methods and routing will be defined in more detail as part of the EIA to identify the most appropriate subsea route and landfall location.
The onshore substation location has yet to be defined and will be subject to a detailed assessment of potential landfalls and optimum locations from both an EIA and final grid connection perspective. There is potential for both the Fair Head and Torr Head tidal projects to share a common substation and grid connection point. This has yet to be confirmed and the ultimate size and voltage of the station will depend on this decision. If both projects are brought into a common point ashore it is likely that the substation will need to transform the voltage of the incoming subsea cables to 110kV.
Vessels to be used in construction have not yet been confirmed, however the project description suggests that jack up barges and DP vessels will be required to install the devices.
Fair Head, Northern Ireland.
Coordinates: 55.231°, -6.107°
An Agreement for lease was granted in 2012. In the lead up to the submission of the planning application (February 2017) feasibility studies for onshore grid connections and baseline studies including those associated with Navigational Risk Assessment were undertaken.
It is proposed that the Fair Head Tidal Energy project could be delivered in phases. FHT is considering an initial demonstration array of around 4 – 6 turbines, and with an output of up to 10 MW, which would be connected into the existing electricity grid at Ballycastle. Further phases would complete the proposed 100 MW array of tidal turbines that would be capable of powering some 70,000 homes.
The Department of Agriculture, Environment and Rural Affairs (DAERA), Northern Ireland, Marine Strategy and Licensing team issues licences for the construction, extension or operation of generating stations under Article 39 of the Electricity (Northern Ireland) Order 1992.
The key environmental issues associated with the project are those common to the tidal stream industry, including:
- Loss of seabed habitat
- EMF impacts
- Barrier to movement
- Vessel disturbance and collision
- Commercial fisheries impacts
Environmental Webpage: http://dpenergy.info/fht/environment
All relevant planning application documents, including EIA docs can be downloaded from the following link: http://dpenergy.info/fht/downloads